1. Field of the Invention
The present invention relates to a bumper device for vehicles and a bumper stay structure therefor.
2. Description of the Related Art
Conventionally, there has been known a bumper device which is disclosed for example in Japanese Patent Laid-open publication No. 58550/2001.
FIG. 6 shows a bumper device 100 which constitutes such a prior art. The bumper device 100 includes a reinforcement member 130 which extends in the lateral direction of a vehicle and both end portions of the reinforcement member 130 is mounted on front end portions of side frames 150 of the vehicle by way of stays 140 which are fixedly secured to the reinforcement member 130.
Further, as shown in FIG. 6, when an impact force which exceeds a given value acts on the bumper device 100, the bumper device 100 makes the stays 140 and the reinforcement member 130 deformed into shapes as indicated by a chain double-dashed line so as to absorb impact energy whereby an impact force applied to an occupant can be lightened.
To absorb the impact energy by surely deforming the stays 140 when the impact force exceeding a given value acts on the bumper device 100, the strength of the stay 140 against the impact force is set smaller than the strength of the side frame 150 against the impact force.
Accordingly, in the known example, a width xe2x80x9cdxe2x80x9d of the stay 140 is set narrower than a width xe2x80x9ccxe2x80x9d of the side frame 150. Due to such a constitution, the stay side is deformed earlier than the side frame 150 and hence, it is possible to prevent the initial deformation from being generated at the vehicle side such as the side frame 150 or the like.
However, since the reinforcement member 130 is supported on the stays 140 having the narrow width, the deformation of the reinforcement member 130 is generated in a shape indicated by the chain double-dashed line shown in FIG. 6 and hence, the range of deformation is limited to peripheries of the stays 140 having the narrow width. In the method in which the given impact energy is absorbed by deforming the reinforcement member 130 in such narrow portions, it is necessary to set a load which is required for deformation of a unit area of the deformed portion to a large value. That is, a thickness of ribs or the like arranged in the inside of the reinforcement member 130 must be increased so as to increase the strength of the reinforcement member 130 in the deforming direction. Accordingly, there arises a problem that the weight of the reinforcement member 130 is increased.
In view of such circumstances, it is an object of the present invention to provide a bumper device which can sufficiently absorb given impact energy while making a weight of a reinforcement member smaller than that of a conventional reinforcement member.
For achieving such an object of the present invention, there is provided a bumper device including a reinforcement member which extends in the widthwise direction of a vehicle and stays which mount the reinforcement member to a structural body of the vehicle, wherein the improvement is characterized in that each stay includes a pair of first mounting portions which are connected to the reinforcement member and a pair of second mounting portions which are connected to the structural body, a width between the pair of first mounting portions is set greater than a width between the pair of second mounting portions in the widthwise direction of the vehicle, and each stay further includes at least a pair of longitudinal walls which connect the first mounting portions and the second mounting portions such that a distance between the longitudinal walls is expanded from the second mounting portions to the first mounting portions in the widthwise direction of the vehicle.
Due to such a constitution, when an impact force acts on the bumper device, the deformation is generated in a wide range of the reinforcement member so that given impact energy is absorbed.
Further, according to the present invention, in a bumper stay which is arranged between a reinforcement member extending in the widthwise direction of a vehicle and a side frame at a body side, the bumper stay is formed of a pressed or press molded product made of a sheet of steel plate and includes a plurality of ribs which extend in a spaced-apart manner in the forward and rearward direction of the vehicle, a connecting wall portion which connects one ends of respective ribs, and mounting lugs which are provided to one ends of inner and outer ribs in the widthwise direction of the vehicle whereby it is possible to provide a bumper stay for vehicle in which a hollow portion between respective ribs opens in the forward and rearward directions.
The bumper stay is molded from a sheet of steel plate and has the mounting lugs extended in the sideward directions from inner and outer ribs thereof and hence, it is possible to make the size between the mounting lugs greater than the size between the mounting portions to side members. The use of steel plate enables arbitrary selection of the inclination of the ribs and the arbitrary adjustment of the strength based on the plate thickness.
According to the present invention, in a bumper stay which is arranged between a reinforcement member extending in the widthwise direction of a vehicle and a side frame at a vehicle side, the bumper stay is formed of an extruded member made of aluminum alloy material and includes a front wall portion and a rear wall portion which extend in the widthwise direction of the vehicle and are spaced apart from each other and at least four ribs which connect the front and rear wall portions, the ribs form at least three hollow portions, the front wall portion is made longer than the rear wall portion in the widthwise direction of the vehicle, and both sides of the front wall portions form mounting lugs, whereby a bumper stay for vehicle in which the ribs disposed at the inside of the vehicle are inclined inwardly and the ribs disposed at the outside of the vehicle are inclined outwardly.
According to this bumper stay, since the front wall portion is made longer than the rear wall portion in the widthwise direction of the vehicle and the inner and outer ribs are inclined, a contact surface between the reinforcement member and the bumper stay can be increased so that it is possible to prevent a local deformation of the reinforcement member at the time of collision.
In this specification, the description is made with respect to a case that the reinforcement member (bumper reinforcing member) is arranged at the front side of the vehicle and hence, the xe2x80x9cfront sidexe2x80x9d means the front side of the vehicle and the xe2x80x9crear sidexe2x80x9d means the rear side of the vehicle in this specification. However, in a case that the reinforcement member (bumper reinforcing member) is arranged at the rear side of the vehicle, the xe2x80x9cfront sidexe2x80x9d means the rear side of the vehicle and the xe2x80x9crear sidexe2x80x9d means the front side of the vehicle in this specification. That is, the present invention includes both examples.